High B-value Diffusion MR Imaging In The Evaluation Of Cerebral Gliomas

PART I:Qualitative Assessment of Gliomas grade:Comparison DWI at b= 3000s/mm2 and DWI at b=1000s/mm2Purpose:To assess whether DWI at b= 3000s/mm2 is more useful in discriminating high-grade and low-grade gliomas than DWI at b=1000s/mm2 by qualitative assessment.Materials and Methods:DWIs at both b=1000s/mm2 and b=3000s/mm2 were performed at 1.5T MR in 73 patients (47 males,26 females; age range,14-70; mean age,44.6years), including 30 low grade gliomas(LGG:G1?G2) and 43 high grade gliomas(HGG:G3?G4). Visual assessment is based on 5-point scaled evaluations. DWI signal intensity ratio (rSI=tumor SI/normal WM SI) and apparent diffusion coefficient (ADC) values were compared between DWIs at b=1000s/mm2 and 3000s/mm2. Student t test, paired t test and receiver operating characteristic analysis were used for statistical evaluation.Results:By visual assessment, DWI at b=3000s/mm2 showed more conspicuous hyperintensity in high-grade gliomas and iso- or hypointensity in low-grade gliomas than DWI at b=1000s/mm2. Sensitivity, Positive and negative predictive values at b=3000 s/mm2 were higher than that at b =1000s/mm2 (88%,84.4%,82.1% vs 62.8%,79.4%,59%, respectively). The mean rSI of high-grade gliomas was significantly higher than that of low-grade gliomas at both b-values (P<0.001). The difference between the mean rSI of high-grade and low-grade gliomas was significantly larger at b=3000s/mm2 than that at b=1000s/mm2. The mean ADC value of high-grade gliomas was significantly lower than that of low-grade gliomas at both b-values (P<0.001). Compared with b=1000 s/mm2 DWI, the mean ADC value of high-grade gliomas decreased by 36%, while the mean ADC value of low-grade gliomas decreased by 26%.Conclusion:DWI at b=3000s/mm2 is more useful than DWI at b=1000s/mm2 in discriminating high-grade and low-grade gliomas at 1.5T MR. PART II:Quantitative Assessment of Gliomas Grade:Comparison the Minimum ADC Value of DWI at b= 3000s/mm2 and that of DWI at b=1000s/mm2Purpose:To assess whether the minimum apparent diffusion coefficient of DWI at b= 3000s/mm2 (minADC:3000) is more useful in discriminating high-grade and low-grade gliomas than that of DWI at b=1000s/mm2 (minADC1000), with quantitative histopathological features of resected tumor tissue.Materials and Methods:DWIs at both b=1000s/mm2 and b=3000s/mm2 were performed at 1.5T MR in 81 patients((51 males,30 females; mean age, 44.4years), including 31 low grade gliomas (LGG) (G1:3; G2:28) and 50 high grade gliomas(HGG) (G3:21; G4:29). On ADC maps derived from DWI of both b values, the minADC value of each tumor was preoperatively determined from several regions of interest defined in the tumor, avoiding cystic, necrotic, hemorrhagic or calcific components. Surgical intervention was undertaken in all cases. The Ki-67 labeling index (LI) were measured in surgical specimen. Mann—Whitney U test, one-way ANOVA, Dunnett's T3, correlation analysis and receiver operating characteristic analysis were used for statistical evaluation.Results:The mean value of minADC1000 for LGGs[(1.279±0.270)×10-3mm2/s] was higher than that of G3[(0.92±0.201)×10-3mm2/s] (P?0.001), and than that of G4[(0.797±0.156)×10-3mm2/s] (P?0.001). But there was no significant difference between the mean value of minADC1000 of G3 and that of G4 (P=0.069). The mean value of minADC3000 for LGGs[(0.940±0.175)×10-3mm2/s] was higher than that of G3[(0.609±0.116) X 10-3mm2/s](P<0.001) and than that of G4[(0.482±0.091)×10-3mm2/s] (P?0.001). There was significant difference between the mean value of minADC3000 of G3 and that of G4 (P=0.001). There were significant negative correlation between minADC1000 and different tumor grades (r=—0.699, P?0.001), between minADC3000 and different tumor grades (r=—0.827, P?0.001). There was significant positive correlation between Ki-67 LI and different tumor grades (r= 0.843, P?0.001). There were negative correlation between minADC1000 and Ki-67 LI (r=—0.555, P?0.001), and between minADC3oooand Ki-67 LI (r=—0.646, P?0.001).Conclusion:The minimum apparent diffusion coefficient of DWI at b= 3000s/mm2 (minADC3000) is more useful than that of DWI at b=1000s/mm2 (minADC1000) in differentiating among glioma grades.Part III:Biexponential Parameterization of Multi b-value DWI in Peritumoral Edema Regions of Glioblastomas and MetastasesPurpose:To distinguish glioblastomas from metastases by assessing the role of multi b-value diffusion weighted imaging in the characterization of the physicochemical properties of the water offered by biexponential model in peritumoral edema regions.Materials and Methods:DWIs at 1.5T MR in 18 patients pathologically proved glioblastomas (10 males,8 females; age range,27-70; mean age, 51.1 years), and 15 metastases (8 males,7 females; age range,38-73; mean age,56.3 years) were performed by using multiple b values. The Dfast Dslow?Ffast values of immediate peritumoral regions and contralateral white matter were measured in each patient. Student t test and paired t test were used for statistical evaluation.Results:There was no significant difference of the mean value of Dfast?Dslow?Ffast between the normal white matter of two groups ((1.329±0.041)×10-3mm2/s vs(1.369±0.169) X 10-3mm2/s,P=0.489; (0.232±0.056)×10-3mm2/s vs (0.251±0.055), P=0.316; (0.647±0.057) vs (0.659±0.059), P= 0.56)). The mean value of Dfast?Dslow?Ffast of peritumoral edema regions of both tumor groups were higher than that of lateral normal white matter (P?0.001). The mean value of Dfast of metastasis group was higher than that of glioblastoma group ((1.884±0.117)×10-3mm2/s vs (1.719±0.246)×10-3mm2/s, P=0.001?0.05). The mean value of Ffast of metastasis group was higher than that of glioblastoma group ((0.893±0.037) vs (0.806±0.047), P?0.001). There was no significant difference of the mean value of Dslow between the two groups ((0.464±0.08)×10-3mm2/s vs (0.439±0.09) X 10-3mm/s, P=0.397)Conclusion:Multi b-value DWI can furnish a detailed characterization of different type of peritumal edema, and may provide a new quantitative approach for the differentiation of glioblastoma and metastasis on the basis of the physicochemical properties of the water molecules in the peritumoral edema.Part?: Preliminary Study of Intravoxel Water Diffusion Heterogeneity Imaging Offered by Stretched-Exponential Model of Multi b-value DWI In GlioblastomasPurpose:To determine the potential value of intravoxel water diffusion heterogeneity imaging offered by stretched-exponential model for brain tumor characterization, by comparing an established heterogeneity index (a value) measured in glioblastomas to those of normal appearing white matter and basal ganglia.Materials and Methods:DWIs at 1.5T MR in 18 patients pathologically proved glioblastomas (10 males,8 females; age range,27-70; mean age, 51.1 years) were performed by using multiple b values. The a and DDC values of the solid elements of glioblastomas and contralateral white matter and basal ganglia were measured in each patient. Student t test were used for statistical evaluation.Results:The mean value of a of glioblastomas were lower than that of lateral normal white matter ((0.61±0.08) vs (0.73±0.04), P<0.001), and lower than that of lateral basal ganglia ((0.61±0.08) vs (0.79±0.06), P<0.001).The mean value of DDC of glioblastomas were higher than that of lateral normal white matter ((1.579±0.296) X 10-3mm2/s vs (0.738±0.043)×10-3mm2/s, P<0.001)), and higher than that of lateral basal ganglia ((1.579±0.296)×10-3/s vs (0.643±0.064)×10-3mm2/s, P?0.001).Conclusion:The heterogeneity index a offered by stretched exponential model of multi b-value DWI is different from those of normal brain structures, which potentially offers a new method for evaluating brain tumors. The physiological mechanism of DDC requires further investigation.